The velocity ratio of a machine is 5 and its efficiency is 75%. What effort would be needed to lift a load of 150N with the machine?
A
20N
B
30N
C
40N
D
50N
Verified Correct Answer: C.
Step-by-Step Mathematical Solution
Efficiency = \(\frac{\text{M.A}}{\text{V.R}}\)
75% = \(\frac{\text{M.A}}{\text{V.R}}\)
\(\frac{75}{100} = \frac{\text{M.A}}{5}\)
M.A = \(\frac{75(5)}{100}\) = 3.75
But M.A = \(\frac{\text{Load}}{\text{Effort}}\)
3.75 = \(\frac{150}{\text{Effort}}\)
Effort = \(\frac{150}{3.75}\)
Effort = 40N
Source: Myschool Past Questions Archive (Record #694)